The day before, Billy Hartman had murdered Kim Sterling. Even though he had no real reason, no motive, no idea who she was. He’d never killed anyone before, never really wanted to. He wasn’t a murderer, wasn’t a beast or a monster. He was a little man with a little life and less ambition. A small cog in a small wheel in a small company that no-one else gave a damn about. But he woke up that morning with murder on his mind, and he couldn’t seem to shift it. He wanted to kill a beautiful woman . . . like all the ones who’d laughed at him, or spurned him, or worse still, ignored him. He wanted to hurt one of them the way they had hurt him. To strike back, just once, and let them feel the pain.

So he took a big knife from his tiny kitchen in his shabby little flat and went out into the great big world, humming cheerfully. He descended into the Underground, and travelled up and down the lines, switching from platform to platform until finally . . . he saw her. And knew immediately that she was the one. He’d thought it would be a hard thing, a difficult thing, to actually kill another human being; but when the time came, he walked up behind her, stabbed her once in the back, and walked away. No-one saw or suspected him. Why should they? He was far too small and unimportant to be noticed. He went back to his flat, still humming cheerfully, made himself a meal-for-one in his little microwave, watched television, and went to bed.

To dream of how it felt when the blade went in, and he twisted it, before withdrawing. He didn’t enjoy it. It felt like someone else’s dream.

But this morning, a new feeling had driven him from his bed. The feeling that something had gone wrong. The morning news said that Oxford Circus Tube Station had been shut down, and serious news presenters said the word murder in their serious voices. And suddenly Billy knew he had to go back, that he had to go back down into the Underground and make sure there was no evidence left to link him to the crime. He couldn’t have anyone finding out what he’d done. That would be awful.

Sneaking back in had proved surprisingly easy. On any other day the massed forces of uniformed police and security guards would have intimidated him into a frozen panic; but not that day. He walked right past them, and they never saw him. Partly because he was, after all, a small and insignificant person, but also because Someone was looking out for him. He could feel it. Someone big and powerful was protecting him.

He walked right past them, right under their noses, and they couldn’t see him.